Conventionally, display devices that achieves display by utilizing a moving phenomenon of a transparent or colored liquid have been suggested. For example, display devices of electric field induction types that utilize an external electric field to move a liquid, thereby displaying information, include those of an electroosmosis system and of an electrowetting system.
In the display devices of the electroosmosis system, a liquid impregnation rate of a surface of a porous body is controlled so as to scatter external light, whereby a light reflectance and a light transmittance thereof with respect to the external light are controlled. Also, these display devices of the electroosmosis system have a configuration in which the porous body and the transparent liquid that have an equal refractive index are prepared in advance so as to achieve transparency by filling the liquid in through holes (small holes) in the porous body and cause light to be scattered by allowing the liquid to flow out from the through holes.
In the display devices of the electrowetting system, an electric field is applied to a liquid inside small holes so as to vary an interfacial tension of the liquid, thus causing this liquid to move by an electrocapillary phenomenon (an electrowetting phenomenon). More specifically, when a switch between a pair of electrodes provided on an inner surface of a small hole is closed so as to apply an electric field to the liquid, a wettability of the liquid with respect to the inner surface of the small hole varies. Accordingly, a contact angle of the liquid with respect to the inner surface of the small hole decreases, so that the liquid moves inside the small hole. On the other hand, when the switch is opened to stop the application of the electric field to the liquid, the wettability of the liquid with respect to the inner surface of the small hole varies, thus increasing the contact angle sharply, so that the liquid flows out from the small hole.
In order to display moving images in the display devices described above, the liquid has to be moved inside the small hole at a high speed and at a low voltage. When the electroosmosis system and the electrowetting system are compared in this respect, the electrowetting system is more suitable for displaying moving images because it can move the liquid at a higher speed.
Further, using the conventional display devices, image displays utilizing the electrowetting phenomenon are provided as described in Patent Document 1 identified below, for example. This display device of the first conventional example is provided with three transparent sheets that are arranged apart from and in parallel with one another, and the transparent sheet positioned in the middle is provided with a plurality of storage cases that are filled with a polar liquid. And, in this display device of the first conventional example, an electric field is applied to the plurality of the storage cases selectively so as to transfer the polar liquid from the corresponding storage cases toward an inside of a space on the display surface side, thereby displaying colored images.
Moreover, other examples of the conventional display device utilizing the electrowetting phenomenon include an image display described in the below-identified Patent Document 2. In this display device of the second conventional example, for example, in an existing transmission-type liquid crystal display, a filter containing a colored liquid is disposed instead of a polarizing plate and a color filter so as to increase a brightness. Moreover, in this display device of the second conventional example, by arranging a plurality of filters in a layered structure, sub-pixels arranged in the same plane can be omitted, and a resolution can be increased, so that the electrowetting phenomenon is utilized as a method for moving the colored liquid in each filter.    Patent document 1: JP 11 (1999)-119703 A    Patent document 2: JP 2004-110041 A